The invention relates to a power nutrunner of the type having a planetary type reduction gearing and a torque limiting release clutch.
In particular, the invention concerns a power nutrunner in which the release clutch is disposed between a ring gear included in the reduction gearing, wherein a first cam means is provided on the ring gear, a second cam means is provided on an annular thrust element, two or more rolling elements are located between the thrust element and the ring gear to engage the first and second cam means, and a spring means is arranged to exert an axial bias load on the thrust element to maintain a torque transferring engagement between the first and second cam means.
A power nutrunner of the above type is previously described for instance U.S. Pat. No. 3,834,467. The nutrunner shown in this patent comprises a planetary reduction gearing having a rotatable but axially immovable ring gear, and a torque limiting release clutch including a spring biassed thrust element as well as cam means on the thrust element and the ring gear.
A significant feature of this known nutrunner is its relatively large axial dimensions. This is due to the fact that the release clutch including the thrust element is located axially separated from the ring gear. The result is a rather long tool housing. However, this is not a drawback in the type of tools illustrated in this patent, namely an angle nutrunner, because a long tool housing with a widely offset tool handle promotes an easier reaction torque counteraction by the operator.
In contrast to angle nutrunners, a straight pistol type tool need to be shorter in order to enhance a comfortable and effective handling of the tool as well as to reduce weight. The problem to which the invention is a solution arises when using this previously known type of reduction gearing/clutch mechanism in a pistol type tool. The axial dimension of the tool housing tends to be too large to meet the demands for a handy tool.
The main object of the invention is to provide a power nutrunner of the above described type in which the reduction gearing/clutch mechanism is axially very compact in order to keep down the overall lenght of the tool.
Other objects and advantages of the invention will appear prom the following specification and claims.
A preferred embodiment of the invention is below described in detail with reference to the accompanying drawing.